This invention relates generally to computer and telecommunications networks and more particularly to a method and apparatus for communication between network devices operating at different frequencies.
Manufacturers of network equipment encounter increasingly complex data transfer design issues as networks and network devices have evolved into sophisticated systems. An increasing number of network systems now utilize a synchronous transfer mode (ATM) technology, which in many applications provides a more effective way to transfer data across a network.
ATM is a layered architecture allowing multiple services like voice, data, and video to be mixed over the network. Three lower level layers have been defined to implement the features of ATM. An Adaptation Layer assures the appropriate service characteristics and divides all types of data into a 48 byte payload that will make up an ATM cell. An ATM Layer takes the data to be sent and adds a 5 byte header information that assures the cell is sent to the right connection. A Physical Layer defines the electrical characteristics in network interfaces. This layer performs necessary operations to effect transmission of data along the transmission media. However, ATM is not tied to a specific type of physical transport.
A number of protocols exist for transmission of information between the ATM Layer and the Physical layer. One such protocol is the Universal Tests and Operation Physical Interface for ATM (UTOPIA) data path interface. UTOPIA defines the interface between the Physical Layer and upper layer modules such as the ATM Layer. The definition allows a common physical interface in ATM sub-systems across a wide range of speeds and media types. UTOPIA controllers are physical devices that implement the UTOPIA protocol for transmitting information between the physical layer and the ATM layer. A UTOPIA I controller is capable of controlling a single slave device, and a UTOPIA II controller is capable of controlling a plurality of slave devices.
One problem with traditional networks utilizing a UTOPIA II controller, or interface, is that many slave controllers run at a maximum rate that is less than the rate at an associated master controller operate. This problem is conventionally added by slowing the master controller to the rate of the lowest slave controller. Such a procedure however, slows down the overall performance of the circuit required to convert the ATM layer side UTOPIA interface to a physical layer device at a lower frequency.
Accordingly, a need has arisen for a method and apparatus for communication between network devices operating at different frequencies. The present invention provides a method apparatus for communication between network devices operating at different frequencies that addresses shortcomings of prior systems and methods.
According to one embodiment of the invention, a method for communicating information in a communication network having a first high speed device, a second high speed device, and a low speed device includes transferring data between the first high speed device and the second high speed device at a first rate and transferring data between the first high speed device and the low speed device at a second rate different from the first rate. Transferring data between the first high speed device and the low speed device at a second rate different from the first rate includes receiving at the first rate, at a buffer system, data from the first high speed device and transmitting at the second rate, to the low speed device, data from the buffer system. Transferring data between the first high speed device and the low speed device at a second rate different from the first rate also includes receiving at the second rate, at the buffer system, data from the low speed device and transmitting at the first rate, to the high speed device, data from the buffer system.
According to another embodiment of the invention, an apparatus for facilitating communication in a network between a first network device operable to receive and transmit data at a first frequency and a second network device operable to receive and transmit data at a second frequency includes a buffer system and a state machine system. The state machine stores in the buffer system, at the first frequency, data from the first network device, and in response, retrieves data from the buffer system, at the second frequency, for providing to the second network device. The state machine system also stores in the buffer system, at the second frequency, data from the second network device, and in response, retrieves data from the buffer system, at the first frequency, for providing to the first network device.
Embodiments of the invention provide numerous technical advantages. For example, the invention allows devices operating at different frequencies to communicate with each other in the same network. Such communication can be facilitated even with the use of xe2x80x9coff-the-shelfxe2x80x9d products that are not easily modified because, according to one embodiment of the invention, a frequency conversion device is provided that does not require modification of existing network devices. Thus, the invention facilitates improved performance of overall bus speed by preventing slower peripherals from slowing down faster devices on the same bus.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.